The present invention relates generally to the field of electrosurgery, and more particularly to surgical devices and methods which employ high frequency electrical energy to treat tissue in regions of the head and neck, such as the ear, nose and throat. The present invention is particularly suited for treating enlarged nasal structures, such as turbinates, polyps or other sinus tissue.
Sinuses are the air-filled cavities insides the facial bones that open into the nasal cavities. Sinusitis is the inflammation of the mucous membranes of one or more of the paranasal sinus cavities. Sinusitis is often associated with a viral or bacterial upper respiratory infection that spreads to the sinuses. When the sinus opening becomes blocked, the cavities fill, producing deep pain and pressure. Postnasal or nasal drainage, nasal congestion with pressure, headaches, sinus infections and nasal polyps are most commonly associated with chronic sinusitis.
Treatment of mild sinusitis typically involves antibiotics, decongestants and analgesics, and is designed to prevent further complications. For more severe or chronic sinusitis, surgery is often necessary to return the nose and sinuses to normal function, particularly with patients who have undergone years of allergy treatment and still suffer from sinus blockage, or patients born with small sinuses and nasal passages. Recent developments in the field of endoscopic surgical techniques and medical devices have provided skilled physicians with instrumentation and methods to perform complicated paranasal sinus surgical procedures. Improved visualization of the nasal cavity and the paranasal sinuses, for example, has now made these anatomical areas more accessible to the endoscopic surgeon. As a result, functional endoscopic sinus surgery (FESS) has become the technique of choice in the surgical approach to sinus disease.
Another nasal symptom, runny noses (e.g., allergic rhinitis or vasomotor rhinitis), is typically caused by small shelf-like structures in the nose called turbinates. Turbinates are responsible for warming and humidifying the air passing through the nose into the lungs. When the air contains an irritant, the turbinates react to the airborne particles by swelling and pouring mucus, as if the body were trying to block and cleanse the breading passage. Enlarged turbinates cause the air space through the nasal passages to become restricted. In these cases, it would be desirable to reduce the size of the turbinates to alleviate the constriction.
For temporary relief of swollen turbinates, pharmaceutical treatment, such as decongestant nasal sprays and pills, is often prescribed. These measures, however, have limited effectiveness, and the long term use of such nasal sprays typically makes the problem worse. Moreover, pharmaceuticals, particularly decongestant pills may cause high blood pressure, increase the heart rate and, for some people, cause sleeplessness.
Various surgical techniques exist to treat enlarged turbinates, with different instrumentation and degrees of invasiveness. Scalpels, electrocautery and powered instrumentation, such as microdebrider devices and lasers, have been used to reduce the size of body structures, such as swollen tissue, turbinates, polyps and the like. Microdebriders are disposable motorized cutters having a rotating shaft with a serrated distal tip for cutting and resecting tissue. The handle of the microdebrider is typically hollow, and it accommodates a small vacuum, which serves to aspirate debris. In this procedure, the distal tip of the shaft is endoscopically delivered through a nasal passage into the nasal cavity of a patient, and an endoscope is similarly delivered through the same or the opposite nasal passage to view the surgical site. An external motor rotates the shaft and the serrated tip, allowing the tip to cut the polyps or other swollen tissue responsible for the blockage. Once the critical blockage is cleared, aeration and drainage are reestablished and the sinuses heal and return to their normal function.
While microdebriders have been promising, these devices suffer from a number of disadvantages. For one thing, the tissue in the nasal and sinus cavities is extremely vascular, and the microdebrider severs blood vessels within this tissue, usually causing profuse bleeding that obstructs the surgeon""s view of the target site. Controlling this bleeding can be difficult since the vacuuming action tends to promote hemorrhaging from blood vessels disrupted during the procedure. In addition, the microdebrider often must be removed from the nose periodically to cauterize severed blood vessels, which lengthens the procedure. Moreover, the serrated edges and other fine crevices of the microdebrider can easily become clogged with debris, which requires the surgeon to remove and clean the microdebrider during the surgery, further increasing the length of the procedure. More serious concerns, however, are that the microdebrider is not precise, and it is often difficult, during the procedure, to differentiate between the target sinus tissue, and other structures within the nose, such as cartilage, bone or cranial. Thus, the surgeon must be extremely careful to minimize damage to the cartilage and bone within the nose, and to avoid damaging nerves, such as the optic nerve.
Lasers were initially considered ideal for nasal surgery because lasers ablate or vaporize tissue with heat, which also acts to cauterize and seal the small blood vessels in the tissue. Unfortunately, lasers are both expensive and somewhat tedious to use in these procedures. Another disadvantage with lasers is the difficulty in judging the depth of tissue ablation. Since the surgeon generally points and shoots the laser without contacting the tissue, he or she does not receive any tactile feedback to judge how deeply the laser is cutting. Because healthy tissue, cartilage, bone and/or cranial nerves often lie within close proximity of the sinus tissue, it is essential to maintain a minimum depth of tissue damage, which cannot always be ensured with a laser.
Recently, RF energy has been used to treat body structures within the nose and throat, such as turbinates. This procedure, which was developed by Somnus Medical Technologies of Sunnyvale, Calif., involves the use of a monopolar electrode that directs RF current into the target tissue to desiccate or destroy portions of the tissue. Of course, such monopolar devices suffer from the disadvantage that the electric current will flow through undefined paths in the patient""s body, thereby increasing the risk of unwanted electrical stimulation to portions of the patient""s body. In addition, since the defined path through the patient""s body has a relatively high impedance (because of the large distance or resistivity of the patient""s body), large voltage differences must typically be applied between the return and active electrodes in order to generate a current suitable for ablation or cutting of the target tissue. This current, however, may inadvertently flow along body paths having less impedance than the defined electrical path, which will substantially increase the current flowing through these paths, possibly causing damage to or destroying surrounding tissue or neighboring nerves.
Another disadvantage of conventional RF devices, such as the Somnus monopolar electrode, is that these devices typically operate by creating a voltage difference between the active electrode and the target tissue, causing an electrical arc to form across the physical gap between the electrode and tissue. At the point of contact of the electric arcs with tissue, rapid tissue heating occurs due to high current density between the electrode and tissue. This high current density causes cellular fluids to rapidly vaporize into steam, thereby producing a xe2x80x9ccutting effectxe2x80x9d along the pathway of localized tissue heating. Thus, the tissue is parted along the pathway of evaporated cellular fluid, inducing undesirable collateral tissue damage in regions surrounding the target tissue site. This collateral tissue damage often causes indiscriminate destruction of turbinate tissue, resulting in the loss of the proper function of the turbinate.
The present invention provides systems, apparatus and methods for selectively applying electrical energy to structures in the head and neck of a patient""s body, such as tissue within the ear, nose and throat. The systems and methods of the present invention are particularly useful for ablation and hemostasis of swollen or enlarged tissue structures in the nose, such as turbinates.
The method of the present invention comprises positioning an electrosurgical instrument adjacent an enlarged body structure so that one or more electrode terminal(s) are brought into at least partial contact or close proximity with the body structure. High frequency voltage is applied between the electrode terminal(s) and one or more return electrode(s) to volumetrically remove at least a portion of the body structure. The electrode terminal(s) may be translated relative to the body structure during or after the application of electrical energy to sculpt a void within the body structure, such as a hole, channel, stripe, crater, or the like. In some embodiments, the electrode terminal(s) are axially translated toward the body structure to bore one or more channel(s) or hole(s) through a portion of the structure. In other embodiments, the electrode terminal(s) are translated across the body structure to form one or more stripe(s) or channel(s). In most embodiments, electrically conducting fluid, such as isotonic saline, is located between the electrode terminal(s) and the body structure. In the bipolar modality, the conducting fluid generates a current flow path between the electrode terminal(s) and one or more return electrode(s). High frequency voltage is then applied between the electrode terminal(s) and the return electrode(s) through the current flow path created by the electrically conducting fluid.
In one aspect of the invention, a method is provided for reducing the volume of enlarged swollen tissue in the patient""s nose, such as swollen nasal tissue, mucus membranes, turbinates, polyps, neoplasms or the like. In particular, a turbinate is treated by positioning one or more electrode terminal(s) adjacent to the turbinate, and delivering electrically conductive fluid, such as isotonic saline, to the nasal cavity to substantially surround the electrode terminal(s) with the fluid. Alternatively, a more viscous fluid, such as an electrically conductive gel, may be applied to the target site such that the electrode terminal(s) are submerged within the gel during the procedure. In both embodiments, high frequency voltage is applied between the electrode terminal(s) and one or more return electrode(s) to remove a small tissue segment, channel or hole from the region near or in the turbinates to shrink the turbinates and prevent swelling, due to the formation of scar tissue as the wound heals. The high frequency voltage may be selected to effect a small amount of thermal damage to the walls of the channel or hole to facilitate the formation of scar tissue without extending this thermal damage beyond the immediate region of the target site.
The hole(s) or channel(s) formed by the present invention, typically less than 3 mm diameter, preferably less than 1 mm in diameter, help to shrink the turbinates and prevent swelling. In an exemplary embodiment, an incision is performed (i.e., with a separate instrument, or with the electrosurgical probe of the present invention), so that the mucosa can be lifted before ablating the underlying tissue. This helps to preserve the mucosa and its important function to the nose. Alternatively, the holes may be made directly through mucosa, which should not adversely affect mucosal transport given the small size of the holes formed by the present invention. A more complete description of electrosurgical methods for forming holes or channels in tissue can be found in U.S. Pat. No. 5,683,366, previously incorporated herein by reference.
In a specific configuration, the nasal tissue is removed by molecular dissociation or disintegration processes. In these embodiments, the high frequency voltage applied to the electrode terminal(s) is sufficient to vaporize an electrically conductive fluid (e.g., gel or saline) between the electrode terminal(s) and the tissue. Within the vaporized fluid, a ionized plasma is formed and charged particles (e.g., electrons) are accelerated towards the tissue to cause the molecular breakdown or disintegration of several cell layers of the tissue. This molecular dissociation is accompanied by the volumetric removal of the tissue. The short range of the accelerated charged particles within the plasma layer confines the molecular dissociation process to the surface layer to minimize damage and necrosis to the underlying tissue. This process can be precisely controlled to effect the volumetric removal of tissue as thin as 10 to 150 microns with minimal heating of, or damage to, surrounding or underlying tissue structures. A more complete description of this phenomena is described in commonly assigned U.S. Pat. No. 5,683,366.
The present invention offers a number of advantages over current microdebrider and laser techniques for nasal surgery. The ability to precisely control the volumetric removal of tissue results in a field of tissue ablation or removal that is very defined, consistent and predictable. Controlling the depth of tissue allows the physician to form a precise channel or hole through the turbinate tissue. This precise heating also helps to minimize or completely eliminate damage to healthy tissue structures, cartilage, bone and/or cranial nerves that are often adjacent the target sinus tissue. In addition, small blood vessels within the nose are simultaneously cauterized and sealed as the tissue is removed to continuously maintain hemostasis during the procedure. This increases the surgeon""s field of view, and shortens the length of the procedure. Moreover, since the present invention allows for the use of electrically conductive fluid (contrary to prior art bipolar and monopolar electrosurgery techniques), isotonic saline may be used during the procedure. Saline is the preferred medium for irrigation because it has the same concentration as the body""s fluids and, therefore, is not absorbed into the body as much as other fluids.
Apparatus according to the present invention generally include an electrosurgical probe or catheter having a shaft with proximal and distal ends, one or more electrode terminal(s) at the distal end and one or more connectors coupling the electrode terminal(s) to a source of high frequency electrical energy. For treating swollen turbinates, the distal end portion of the shaft will usually have a diameter of less than 3 mm, preferably less than 1 mm, to facilitate the formation of small hole(s) or channel(s) within the swollen turbinate tissue. The shaft may additionally include a lens at the distal end coupled to a proximal eye piece for endoscopically viewing the target tissue.
Alternatively, the endoscope may be a separate instrument that is introduced through the same or a different opening as the electrosurgical probe.
The apparatus will preferably further include a fluid delivery element for delivering electrically conducting fluid to the electrode terminal(s) and the target site. The fluid delivery element may be located on the probe, e.g., a fluid lumen or tube, or it may be part of a separate instrument. Alternatively, an electrically conducting gel or spray, such as a saline electrolyte or other conductive gel, may be applied the target site. In this embodiment, the apparatus may not have a fluid delivery element. In both embodiments, the electrically conducting fluid will preferably generate a current flow path between the electrode terminal(s) and one or more return electrode(s). In an exemplary embodiment, the return electrode is located on the probe and spaced a sufficient distance from the electrode terminal(s) to substantially avoid or minimize current shorting therebetween and to shield the return electrode from tissue at the target site.
In a specific configuration, the electrosurgical probe will include an electrically insulating electrode support member having a tissue treatment surface at the distal end of the probe. One or more electrode terminal(s) are coupled to, or integral with, the electrode support member such that the electrode terminal(s) are spaced from the return electrode. In one embodiment, the probe includes an electrode array having a plurality of electrically isolated electrode terminals embedded into the electrode support member such that the electrode terminals extend about 0.2 mm to about 10 mm. In this embodiment, the probe will further include one or more lumens for delivering electrically conductive fluid to one or more openings around the tissue treatment surface of the electrode support member. In an exemplary embodiment, the lumen will extend through a fluid tube exterior to the probe shaft that ends proximal to the return electrode.
In another embodiment, an electrosurgical instrument, such as a probe or catheter, comprises a shaft with proximal and distal ends, one or more electrode terminal(s) at the distal end and one or more connectors coupling the electrode terminal(s) to a source of high frequency electrical energy. In this embodiment, the electrode terminal(s) are preferably designed for cutting tissue; i.e., they typically have a distal edge or point. Conventional electrosurgery cuts through tissue by rapidly heating the tissue until cellular fluids explode, producing a cutting effect along the pathway of localized heating. The present invention volumetrically removes the tissue along the cutting pathway in a cool ablation process that minimizes thermal damage to surrounding tissue. The electrode terminal(s) are preferably designed for cutting tissue; i.e., they typically have a distal edge or point. In the exemplary embodiment, the electrode terminal(s) are aligned with each other to form a linear cutting path through the tissue.